Get fast relief of heartburn, upset stomach, acid indigestion with headache or body aches from this effervescent antacid and pain reliever that has been around for more than 80 years. Unlike other antacids, such as Tums or Mylanta, H-2 blockers such as Pepcid, and PPIs like Prilosec, Alka-Seltzer® Original contains an analgesic for pain accompanied by heartburn and acid indigestion.